This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The work I intend to do is a part of a simulation project where I simulate the full maxwell equations to find the near field of 20nm diameter polystyrene beads which has dye molecules in it. To keep the simulation close to the real situation I need to know the complex refractive index of the beads with the dye. The procedure is as follows,First measure the extinction coefficient with the Perkin Elmer UV-Vis absorption spectrometer. Then with the known values of concentration and particle size its possible to relate the measurement to the complex refractive index.